Internal combustion engines having a relatively small number of cylinders provide automobile makers with an attractive response to the need for improved fuel economy. In order to compensate for a reduction of cubic engine capacity, vehicle manufacturers developed technologies to improve engine power, such as direct fuel injection, turbocharging, and variable timing for inlet and exhaust camshafts. In this way six- and eight-cylinder engines can be scaled down without losing available horsepower.
An undesirable consequence of engines with a small number of cylinders is high crankshaft torsional vibration and high engine block vibration caused by forces, such as first and second order forces, that are not cancelled. Such vibrations are ultimately transmitted through the engine mounts and driveline to the vehicle structure.
Engineers managed these vibrations to one extent or another through a variety of approaches, many of which increase the cost of construction and reduce fuel economy. One accepted solution to overcome excessive vibration is the provision of one or more pendulums on the crankshaft to lower the torsional vibration of the crankshaft and the consequent driveline vibration. Such crankshaft-mounted pendulums function as vibration absorbers as they are tuned to address and thus cancel out vibrations generated by crankshaft rotation, thus smoothing torque output of the crankshafts. This approach is taken as well by designers of some airplane piston engines where the pendulums smooth output torque and reduce rigid body motion.
Pendulum vibration absorbers are attached to the engine crankshaft web using pendulum carriers. The pendulum carriers are themselves attached to the crankshaft web according to a wide variety of attachment methods, including mechanically fastening. In many instances, the crankshaft itself requires excessive machining to accommodate the pendulum carrier.
While the concept of attaching a pendulum to a crankshaft provides smoother engine performance, known methods of attaching the crankshaft pendulum carrier to the crankshaft are overly complex, resulting in either expensive pendulum carrier production or expensive crankshaft preparation or both. Accordingly, a new approach to the attachment of the pendulum carrier to the crankshaft web is needed to address the problems associated with known arrangements without compromising the desired reduction of torsional vibration produced by the internal combustion engine.